Floods that prevented timely cotton planting will push planting of the 2011 cotton crop later than what is normal. Here are a few tips to make a late planted crop as productive as possible.
Plant Population: Don’t cut seeding rates. The thinner the plant stand the more ‘bushy’ and later maturing the crop will become. A target 2.5-4.0 plants per row foot (34,000-54,000 plants per acre) will be optimal. Remember that you rarely achieve a 100% stand so planting 2.5 seed per foot will not guarantee a stand of 2.5 plants per foot.
Fertility: Adequate potash levels will help boll filling in early maturing varieties and prevent deficiency symptoms. Excessive phosphorous can cause thin stalks which will lead to lodging. Nitrogen should be applied at no more than 60 lbs N per acre on bottom soils and no higher than 80 lbs per acre on hill ground. If you have a history of high nitrogen use or if you are following a soybean crop, reduce your nitrogen rates by an additional 10-20 lbs per acre. High nitrogen rates will promote rank growth and increase the number of days to maturity. Avoid foliar nitrogen fertilizer applications. These applications can also promote later maturity.
Insect Management: It is funny to talk about cotton growth and development in an insect discussion. However, in planting date trials cotton planted June 1st does not bloom until August 1st. Cotton planted June 15th will bloom around August 10th. August 10th is typically considered the last effective bloom date for most of west Tennessee. This is the date that a white bloom has only a 50% chance to become a harvestable boll. This means you will need to protect all fruiting forms and bolls to achieve top yields.
The three most important items for late planted cotton insect management are: 1) Scouting, 2) Scouting and 3) Scouting. Most varieties contain Bollgard II or WideStrike Bt technologies to help with worm control. As we learned last year these technologies can still have worm damage when pressure is high so keep your scouts in the field. Plant bugs also need to be monitored closely to protect the lower fruit on the plant since this is where the majority of the yield potential will reside on the plant.
Herbicides: Anything that slows plant growth or causes a plant to lose fruit will delay maturity. If you are planning to use Ignite to control pigweeds in WideStrike cotton varieties you may consider keeping the Ignite under hoods to prevent injury to the crop.
Plant Growth Regulators: It is important to identify which fields or portions of fields can become rank if favorable conditions exist. Earliness and growth control are enhanced by early application of mepiquat-type PGRs. Lower rate, multiple applications beginning after matchhead square often give good results. However, applications made near bloom are usually safer because they reduce the risk of prematurely stopping vegetative growth in the event of drought conditions. It is important to remember that low rates are not effective on larger cotton that has become rank. Match the correct rate with the situation at hand; larger cotton will need higher rates. It is difficult to make a PGR recommendation that will cover the needs of all fields, and for that reason, it is important to use a program tailored to the individual field.
Irrigation: Base irrigation timing and amount on crop need. UT research suggests that 1 inch of water from rainfall or irrigation per week starting at or just after first bloom is optimal. A late planted crop that does not have a white flower until the first week of August may require starting irrigation closer to matchhead square while closely monitoring plant growth to prevent excessive vegetative growth. This earlier start time will allow soil moisture to be maintained going into bloom. Termination of irrigation usually coincides with the appearance of the first open boll. In late planted cotton, remember that the crop needs time to ‘dry out’ to promote boll opening (think about how hard it was to open bolls during 2009 with excessive rainfall). It takes around 40-45 days to go from white flower to open boll. If the first white flower appears on August 1st the first open boll will appear in mid-September. Depending on weather conditions and the long term forecast irrigation termination may need to occur prior to appearance of an open boll to promote earliness in late planted cotton.
Foliar Fungicides and Other Foliar Products: UT research has no found a positive effect from the use of foliar fungicides on cotton. The best way to manage boll rot is to prevent the plants from becoming rank by lowering nitrogen rates and correctly using plant growth regulators. Since a late planted crop will have lower yield potential resist the temptation to use products that are not proven effective in University trials to save on input costs helping improve your profitability at the end of the year.
Defoliation and Boll Opening: Don’t chase phantom bolls, especially on a late-planted crop. Defoliation should be timed with harvest of the mature bolls in mind. Addition of an ethephon-based boll opener will increase the percent of the crop picked at first harvest. Keep in mind that ethephon does not promote crop maturity and no amount of ethephon will open small, immature bolls. Ethephon products need at least 50 DD60s to work, and higher rates will be needed under cool temperatures. Defoliants will need to be used at higher rates as late season temperatures decline. An October defoliation will likely be based on herbicidal defoliants and high rates of ethephon.
These are just initial thoughts on managing late planted cotton to help in planning crop management. My best recommendation is to hire a crop consultant or at least hire a scout to keep eyes on your valuable cotton crop. UT will offer a Scout training school in Jackson at the Experiment Station on May 27th. More information can be found here (Scout School) Further advisories will be posted as the growing season progresses.
